As Joost++ points out, the problem in your code is that it checks only for text files (-T), hence not including your executable binary.

Also, if you're trying to create the link on the parent directory, the destination string should read "/home/test/", not "/home/folder" (you should probably not hardcode it like that either, as any typo can bring unexpected bugs like this one. Use you $dir variable! :-)

But what I would really warn you about is on putting the returned value of symlink() back on $file. Not only it destroys your filename for further use, the variable name differing from what it actually does (or any multi-use variable at any rate) will most likely confuse you if your program escalates.

Even worse, if a user tries to run your program on a filesystem that does not support symbolic links, it will cause a fatal error unless you trap it in an eval block. You could do something like:

#!/usr/bin/perl
use strict;
use warnings;

my $dir = "/home/test/folder";
opendir(BIN, $dir) or die "Can't open $dir: $!\n";
my @array = grep { -f "$dir/$_" } readdir BIN;

foreach my $file (@array) {
   eval { symlink ("$dir/$file","$dir/../$file") }; # links to parent
   if ($@) {
      print "could not create symlink for $file\n";
   }
   else {
      print "success!\n";
   }
}
[download]

Of course, if this is just a simple PoC code where you were not particularly concerned with the pointed issues, feel free to ignore them :-)

Hope this helps!